Shortly after about the year 1900, it became possible to sensitize film to red light. This presented the possibility of full color photography and led to color films using a dense matrix of red, green, and blue filters (i.e., color grid), called a “Reseau”. The Reseau is permanently adhered over a panchromatic black and white film (i.e., referred the herein as a Reseau-enhanced panchromatic film). Dufaycolor brand film (i.e., a Dufay film) and Autochrome brand film (i.e., an Autochrome film) are examples of such Reseau-enhanced panchromatic film. The disclosures made herein relate to color film restoration, and particularly to restoration of early color films that use a color grid over an underlying silver film (i.e., silver layer on a film substrate) such as Dufaycolor brand film and Autochrome brand film.
FIG. 1 shows a cross section of a Dufay film 100, which is an example of a Reseau-enhanced panchromatic film (i.e., a color matrix film). The Dufay film 100 is an example of classic Dufay in which a color grid 102 (i.e., a reseau color grid) is assembled on a film base 104 (e.g., a clear film base) in a light room, and then a sensitive emulsion 106 (i.e., a silver layer) is coated over the color grid in the dark. Therefore, exposure is made through the film base 104. As shown in FIG. 1, red light 107 passes through the film base 104 and red cells 108 of the color grid 102, but not blue cells 110 of the color grid 102. The red light 107 exposes the emulsion adjacent to the red cells 108, but not blue cells 110. When the Dufay film 100 is developed as a negative and later viewed, the exposure from the red light (i.e., red light exposure) has caused the sensitive emulsion 106 to appear blue because only light passing through the blue cells is allowed to continue through unexposed (i.e., clear) emulsion. The opposite would happen if the Dufay film were developed as a positive.
FIG. 2 shows the topology of the color grid 102 of the Dufay film 100 in FIG. 1. It can be seen that there is variability in the color grid 102, which manifests as color noise. In addition to the variability, there is one or more relatively large defects 200 where one or more of the colors of the color grid 102 has exceeded its intended bounds.
As an example of the resulting functionality of a Reseau-enhanced panchromatic film, a red dress would expose primarily through the red filters to the film under the red filters. After reversal development, light would pass through the film primarily through the film that was under the red filters and thus through the adhered red filters, and red light would predominate in the view. This method was in use from the century years to the mid-1950s, resulting in the first generation of images of our world in full color, tracking half a century of color imagery. Many of these images are now treasured in artistic and historical archives worldwide.
It is well known that color matrix dots such as that of a Reseau-enhanced panchromatic film are distracting when viewed directly. However, the eye integrates to an extent so the image can still be enjoyed. A special problem arises in the modern world of digital photography because the color matrix is simply not digital friendly. The images can not practically be presented on a modern display in their original form of colored dots, and removing the dots to make them compatible with modern displays leads to further deterioration of the image.
Therefore, techniques for clarifying the aforementioned images with color matrix film and preparing them for modern (e.g., digital) display would be advantageous, desirable and useful.